"bottomless gulf, greatest depths," now chiefly poetic, c. 1300, from Old French abisme "chasm, abyss, depths of ocean, Hell" (12c., Modern French abîme), from Vulgar Latin *abyssimus (source also of Spanish and Portuguese abismo), which represents perhaps a superlative of Latin abyssus or a formation on analogy of Greek-derived words in -ismus; see abyss.